Fire resistant asphalt coating



Patented sep jmfl 2,569,399

lQh lE-ell Frank B. Burns, Chicago, Ill., and Millard S. Lar rison, Frankford, Pa., assignors to United States Gypsum Company, Chicago, 111., a corporation of Illinois No Drawing. Application August 7, 1943,

Serial No. 497,869 Y 7 15 Claims. (01. 106-282) This invention relates to a coating composition combustible material such as asphalt roofing ,felt, I

for surfaces,.which is not only resistant to norwill not only supply adequate protection from mal exposure conditions but also is highly reatmospheric weather conditions but will also be sistant to fire, thereby protecting combustible greatly improved in its resistance to fire. material over whichit may be applied. It is an .object of. this invention to produce a The coating. composition, prepared in accordcoating composition which is non-flowing, flame ance with this inventiion, and whch Will be subresist-ant, plastic and predominantly bituminous sequently described in detail, has many applicain composition, especially suited for the manutions. It is particularly adapted for use in asfeature of covering elements of he composition phalt compn a. protective coating. 10 type.

The reg ar comcial type of composition It is also 'a further object ofthis invention to roofing, which consists of mineral gr ules a pprovide a Coating composition whi W plied to a surface coating 11 an asphalt satuplied to an especially prepared roofing felt, will rated roofing fe. '5 ill enable the roofing so formed to meet certain Underwriters Laboratories requirements of fire I, v 'fif; U resistance hitherto unttainable in roofing of this ad of supplying a barrier to fire, class. I h it actually aids since it is combustible. It is still further an object of this invention to In order to determine the suitability of roofing provide a coating composition which does not 1 material as a fire barrier, the Underwriters Labflow or run, and which exhibits substantially no i oratories, an organization supported by Fire cracking when subjected to a burning brand or Underwriters, have devised tests to show the fagot for a suificient time to consume the brand merit of a roofing material when in use as a fire or fagot completely.

barrier. These tests areso designed that they Additional objects will occur to those skilled in will bring out the true performance of a roofing 5 the art of which this invention is-a part, 1 material during a fire. There are three tests The coating composition prepared in'accordwhich are known as Burning Brand, Flame ance with this invention is so designed that it 3 Propagation and the Direct Flame tests. becomes a tough, cohesive, continuous inorganic N writers Laboratories, it can be demonstrated or direct flame for a period of time sufiiciently that the coating composition currently used in long to completely burn out the organic conth ma ufa tu f mp s t n r fing wi l stituents of the coating composition. If the heat Under these tests, developed by the Undercovering after it has been once exposed to'heat 3 soften and flow down the roof almost as freely a or fiame is applied for a sufiicientlength of. time as water thus adding fuel o he flame e ow With to burn out all or substantially all of the cementithe continued application of the flame. This is tious organic com sition, there will still remain illustrated best by the Flame Propagation test a, continuous, cefiggve ash, capable of retaining W 3 wherein the burning area spreads rapidly up the it shape andcontinuity evenwhen exposed to I pp ng deck to envelop the ent re a a awind having a velocity up to 12 miles per hour, 1 E1 ered by the composition roofing. This test when it is Supported Ona roof deck having. a l r y ShOWS t e marked d sadvantages of the 40 slope of about 5 inches per lineal foot. This a; p t pe f a p lt mp s i n r f n test is of particular significance since the ash 1 j y t ria Likewise, When h urning Brand test protects the substructure. The composition is is used, he area n er the r nd is ompl y further designed to'resist ,or accommodate therl eroded of protective m n al granules y he fr mal stresses or strains caused by the burning fiOW f e molten roofing phalt. Thus the brand or fagot on the surface of the roofing so i base felt is exposed and offers no further protecthat substantially no cracks develop in the body tion to the structure, of the roof coatin t I i i It is therefore but one of the many objects of In addition, a coatin'g'composition prepared in i this invention to disclose means by which a comaccordance with this invention is well suited for position may be made which, when applied to application to composition roofing, and will not i materially flow on slopes up to 50 degrees when exposed to a direct gas flame having an estimated temperature of approximately 1600 to 1800 degrees Fahrenheit. Also, when granules are applied to this coating, they will adhere to its surface sufficiently so that, during the application of the flame, they will not be removed until substantially all of the cementing organic constituents of the coating composition are destroyed by fire.

This coating composition, when applied to composition roofing, is also-sufficiently fire resistant to inhibit the spread of name up a roof deck even when fanned by a 12 mile per hour wind. The flame spread of this composition meets the Underwriters Laboratories requirements for a class A label service for the Flame Propagation test.

The product of this invention is obtained by a novel combination of a bituminous binding material, such as asphalt, with materials which will tend to form a crust or which will destroy any marked tendency for the asphalt to flow. Not all combinations of these various materials will give effective results, for only. by following the principles set forth inth'is intention can a satisfactory product be obtained. In' practicing this invention, it is necessary to form a proper blend of the waterproof binding, material with the inorganic incrustating'an'd' flow preventing materials. If this is not. done, weather resistance may be sacrificedto obtain the fire protection and the product formed would not have commercial utility. By following the procedure, which will beset forth in the. examples, it is possible for anyone skilled in the art of which this invention isia part, to carry out the essential principles of this inventio n.

In the forthcoming example only three particular types of asphalts are used. It is to be understood that other asphalt ic materials or materials having, equivalent properties can be substituted and will not depart from the scope of this invention. When the words asphalt or asphaltic material are used in thisinvention, it is intendedtopover, by siichterm all bituminous materials as a class which are used or are suitablefor roofing purposes;

Any material which will intumesce and form a crust during heatingand decrease and prevent the flow of, the superheated asphalt is suitable in carrying out the principle of this invention. It has been foundthat, a certain quality and quantity of asbestos servesthe purpose very well when associatedvv with materials such as ground unexpanded vermiculite, ground bituminous coal, capable of coking, though other equivalent materials may be used. satisfactorily. The usual mineral filler incorporated in the common coating ordinarily applied to composition roofing can also be incorporatedin the coating composition made in accordance; with this invention. Adjustments in the amount required can be readily made for the amount of active ingredients used. Eimars such as powdered limestone, flaked slate dust, ground clay, calcined dolomite, etc., can be used. However, it is possible to replace all of this filler material with the crust forming or flow prevention material and still be within the scope of this invention. The active materials may include asbestos, ground bituminous coal, ground unexpanded vermiculite, etc. These materials are blended with the asphalt coating and applied to the surface which is to be protected, such as a saturated roofing felt sheet.

The following examples are given merely as illustrative of various ways of carrying out this invention without in any way limiting the scope thereof.

EXAMPLE 1 Parts by weight Coating asphalt 61.5 Asbestos fiber 15.4 Ground bituminous coal 7.7 Finely ground unexpanded vermiculite 7.7 Diatomite 7.7

EXAMPLE 2 Parts by weight Coating asphalt 61.5 Asbestos fiber 15.4 Ground unexpanded vermiculite 7.7 Finely ground clay 15.4

EXAMPLE 3 Parts by weight Coating asphalt 66.7 Asbestos fiber 16.7 Ground bituminous coal 8.3 Limestone dust 8.3

EXAMPLE 4 Parts by weight Asphalt 50.0 to 61.5 Asbestos fiber 8.4 to 20.0 Ground bituminous coal 12.5 to 15.5 Finely ground mineral fillers 7.5 to 25.0

In all of the examples of coatings given, it will be found that when they are applied to a saturated roofing felt, all willresist flowing and all will form a firm, strong crust when fired. It is not the intention to form a coating which has absolutely no flowability under heat, as it has been found desirable to have a slight amount of this action in order to close and seal the butt edge of the shingles against moisture, wind, etc. When the composition is burned the resulting crust is strongest before; all of the organic matter has been burned out. 'However, the ash formed by any of the above examples will be found to be firm and strong to protect further the supporting structure.

The various ingredients are blended with the molten asphalt in the same manner as now used for incorporating fillers and in conventional equipment, though special equipment like a pug mill may be found more desirable.

The coating asphalt usediin the above examples' has a ring and ball softening point between 210 and 235 F. Other suitable varieties like the steep asphalt have a ring and ballsoftening point between and while the flux asphalt has a ring and ball softening point of 107 F. Other asphaltic materials such as Trinidad asphalt, coal tar pitch, stearine, and other pitches or mixturesv thereof. can be substituted for those given inthese examples. Each source and type of asbestos, coal, filler, etc., used, may require some adjustment in the bituminous materials as to optimum. softeningrange, but this also can readily be. determinedfby those skilled in theart.

In a numberofthe formulas given above, vermiculite in unexpanded form has been used. This material must be handled carefully during the blending and coating stages, for itwill exfoliate when heated too highly. However, it can be used, though other materials such. as coking coals are preferred for a number of reasons.

While it hasbeen. found ,in preparing. coating similar to the examples given above that clay and.

certain other iiltrafine fillers give a Slightly superior fire test performance than those of a coarser nature, yet, because of the matter of higher cost and greater difliculty of properly dispersing this type of powdered filler, it has been found more desirable in commercial practice to use the coarse, regular ground limestone filler. Any type of inorganic filler can be used by making a slight adjustment in the formula. However, it is preferred to use those which have been proven valuable in use in composition roof coatings.

It has been found that ground coal of certain properties and characteristics is extremely desirable in carrying out the purpose of this invention. This coal should be of a bituminous type. Any. coal of this class, which is finely ground, such as about 100% through a 100 mesh screen, and having moderate to strong coking tendencies, can be used for the purpose. A coal known in the trade as the Sewell seam coal has been found to be very satisfactory and is the preferred material.

A typical analysis of this coal as given below, shows that it is a high volatile coal which is particularly characterized by its ability to coke into well formed, strong, nonbrittle agglutinated, coke lumps. It is also characterized by the property of swelling or expanding during the coking" process. Though the Sewell seam of coal runs particularly in Fayette County, West Virginia, the same seam outcrops in other sections, and like the Pocahontas coal, is better known by the name of its geological deposit. Other coals possessing like characteristics may also be used, but the term Sewell seam coal as used herein, illustrates the preferred type of coal.

SEWELL SEAM COAL Typical analysis Moisture per cent. 3.1 Volatile do 22.4 Fixed carbon do v 7.2 Ash do 4.3 Sulfur do 0.1 Heat value B. t. u 14,460

In order to obtain the optimum effectiveness in carrying out the principle of this invention, it has been found that very close attention is required to every detail, particularly as to the par-' ticle size and amount used of each ingredient. For example, it has been found that an accurate grading of the length and quantity of asbestos fiber used will result in improved properties of the coating formed. This coating has met the rigid requirements for the class B- rating. This coating when applied to a mineralized type of roofing felt will even pass some of the requirements. of class A. However, the following Example was found to be even more successful in resisting cracking during the Burning Brand and other fire tests. This material will not crack at all after being subjected to the fire tests, and forms a continuous, strong, hard crust at all times.

EXAMPLE 5 Parts by weight Asphalt (195-200 grade) 50 Ground coking coal (Sewell seam) 14 Asbestos fiber6D grade 10 Asbestos fiber -7K grade 6 Limestone dust In the above examples wherever asbestos is used, grades substantially within the class known as 7K asbestos are intended: This grade is sometimes referred to as Kings D brand. Amosite, a grade of African asbestos, is superior to the 7K type of asbestos in equivalent proportions, and is within the scope of the word asbestos as defined in this invention, for it is not the intention to limit the type of asbestos to 7K only as any equivalent asbestos or mixture of asbestos fillers may be used, for example, such as 6D or a mixture of a higher grade than 7K and a substantially lower grade, but obtaining 7K effect.

The terms 7K and 6D are the standard designations of grades set up by the Quebec Asbestos Producers Association. These grades are more fully set forth in the Canadian Department of Mines Bulletin 707 (1931), and are also described in the U. S. Bureau of Mines Bulletin 403 on Asbestos (1937) at page 70ff. According to this standard grades, a typical 7K fiber would screen as follows and a typical 6D asbestos fiber would screen as follows A standard sample (16 ounces) of asbestos is sifted successively through a nest of screens having openings inch, 4 mesh, and 10 mesh. The first number represents the amount by weight of fiber retained on the inch screen; the second number represents the amount by weight retained on the 4 mesh screen the third represents the amount by weight retained on the 10 mesh screen, and the last number represents the amount in weight passing through the 10 mesh screen. These grades are distinctly fibrous in character. The Quebec Asbestos Producers Association have set up nine (9) groups of asbestos grades. Thus 6D is a grade D in the sixth group. The sixth group contains fibers used in stucco or plaster. The seventh group consists of fibers designated by letters such as 7K and still finer fibers designated by weight per cubic foot such as 7-20, which means that the fiber when loosely packed will weigh 20 pounds per cubic foot. The asbestos sand starts with a'weight of 8-40 or it is in the eight group and weighs about forty pounds per cubic foot.

Thus 7K and letter designations are grades distinctly fibrous in character and far removed from the 8-40 classification. The table given below shows a typical laboratory testing screen analysis made on the fibers of asbestos of the grades 7K and 6D.

TABLE I Typical screen analysis Type 6D 7K 7T 7RF Per Per Per Per cent cent cent cent Retained on 14 mesh 19. 0 8.0 0. 6 0.5 Retained on 48 mesh 63. 0 61. 0 44. 9 30. 0 Retained on mesh.. 5.0 6.0 11.0 20. 5 Retained on 200 mesh 5. 0 10. 0 9. 5 7. 0 Passing thru 200 mesh 8. 0 l. 5 34. 0 42. 0

ences to the various tests of the Underwriters Laboratoriesare those ineiiect an'din'use about Marchl, 1943.

To summarize, the essential principle of this invention is a coating composition made from an asphaltic type binder, a flowprevention material, and a crust forming material which does not liquify sufficiently under the application of :a direct flame to flow from its base when .placed on slopes up to 45 to 50 degrees and which retains in position protectivegranular materials during exposure to flame until substantially all-of the organic binder composition is burned out. This composition will also form a hard, tough, continuous crust-like surface up'on exposure to flame, and after a burn-out, a continuous "cohesive ash capable of withstanding an :air velocity of at least 12 milesper hour is formed. This .protective ash coating further inhibits the :spread of flame upon a roofsurtace even when the flame is fanned by wind up to'lz miles per hour. It will also resist cracking under thermal :stresses and strains set up during the burning of brands or faggot on the surface of roofing covered with this coating composition. 'It not only protects the underlaying-surfacing of combustible material from direct contact with flame, but also prevents cracks through which admit of air might reach into and fan into open flame any glowing area under the ash.

Though the above examples are given as illustrations, it is obvious that various extensions and adaptations can readily be made without departing from the spirit and scope of the principles of this invention as defined in the hereunto appendedclaims.

It is claimed:

1. A weather and fire resistant bituminous coating composition 'for application to a felt base roofing sheet which comprises a vehicle consisting of a bituminous thermoplastic material having intumescible material selected iromstheigroun consisting of unexfoliated vermiculite and coking coals dispersed in said vehicle in sufficient quantity to reduce the flowability-of the bituminous vehicle when it is subjected to flame conditions.

2. The product of claim 1 in which the saidintumescible material -is an unexpanded coking coal.

3. A bituminous coating composition for application to a felt baseroofing sheet which comprises a vehicle consisting of a bituminous thermoplastic material having comminuted unexfoliated vermiculite dispersed therein in sufiicient amount to reduce the flowability of the bituminous vehicle when itis subjected to flame conditions.

i. A weather and fire resistant bituminous coating compositionfor application to a felt base roofing sheet which comprises a vehicle consisting of a thermoplastic asphaltic material, having dispersed therein a filler which comprises a fibrous inorganic material and an intumesciblecrust formingmaterial, which latter material is selected from thegroup consisting of unexfoliated vermiculite and coking coals, the said flller dispersed in said vehicle in sufficient amounts to prevent-the flow of said thermoplastic, asphaltic material under the action of flame conditions.

5. The product of claim a in which the-intumescible material is an unexpanded coking coal. 7

6. A bituminous coating composition for application to a felt base roofing sheet .whichcom- .prises a vehicle consistingore-bituminous thermoplastic material having unexioliated vermicu lite and asbestos flbre dispersed therein in vsuflicient amounts to reduce the flowability of the bituminous vehicle when it is subjected to flame conditions.

7-. A weather resistant, flre retardant coating composition comprising substantially the materials given below and substantially within the ranges given:

Per cent Asphaltic material 50.0 to 61.5

Mineral fiber material 8.0 to 20.0 Intumescible material selected from the group consisting of unexpanded vermiculite and coking coals -r 7.0 to 15.5

Finely .ground mineral filler 7.5 to 25.0

8. The compositionof claim '7 in which the said intumescible material is a coking coal.

9. The composition of claim 7, in which the said intumescible material is unexfoliated vermiculite.

10. The composition of claim 7 in which the said mineral fiber material is asbestos flber selected from the group consisting of 6D and 7K grades.

11. In a flre retardant-asphalt coating composition characterizedby resistance to burning and flow when subjected to flame conditions applied to the said coating when the latter is maintained at an angle not greater than 50 degrees from the horizontal, a bitumen having a softening point of not less than about 185 F. when tested by the rin and ball method, the said bitumen being present in a quantity of not less than fifty per cent by weight of'the said coating, the balance of said coating comprising :not more than forty per cent of a comminuted asbestos fiber which all passes a four mesh screen and of which at least thirty per cent is retained on a forty-eight mesh screen, an intumescible mineral selected from the group consisting-of 'unexpanded coking type bituminous coal and comminuted unexfoiiated vermiculite, and a mineral filler conventionally used in-the art.

12. In-the product of claim 11 wherein at least rflityper center-the quantity-of comminuted asbestos fiber is retained on a loomesn screen.

13. Intheproduct'of claim .11 whereinthe said intumescible material consists 'of Sew l coal as herein described-the said coal beingcomminuted to pass approximately per cent through a 109 mesh screen.

14. The product oiclaimll in'which the said intumescible mineral consists of unexicliated vermiculitepresent'infsaid coating in a quantity not less than 7.5 per cent by weight.

15. In a fire retardant asphalt coating composition characterized by resistance to -fire and flow when subjected to'flame conditions applied to'the said'coating coinpositicnwhen the latter is maintained at an -iangleinot greaterthan fifty degrees from the horizontal, a bitumen havingasoftening point of not .less than about F. when tested by the ring and ball method, the said bitumen being present in a quantity of not less than fifty-per cent by weight of said coating, the balanceofsaid coating composition comprisi. not more than forty: per cent by weight of a filler consisting-of cemminuted asbestos fiber which passesa four mesh screen, and of which at least thirtygper cent is retained on a forty-eight mesh screen, .and sat least twenty-flve percent of said .filler is a -.comminuted-rcoking. intumescible type GU35 fitrrrireuga bituminous coal; and a mineral filler conven- Number tionally used by the roofing industry. 2,125,286

FRANK B. BURNS. 2,128,392 M. S. LARRISON. 2,158,772 5 2,214,904 REFERENCES CITED 2 326 723 The following references are of record in the 2,326,724 file of this patent: 2,333,189 UNITED STATES PATENTS m 2356,87 Number Name Date 2,113,794 Leaute Apr. 12, 1938 Number 2,124,843 Anderton July 26, 1938 488,039

Name Date Fletcher Aug. 2, 1938 Albion Aug. 30, 1938 Beckwith May 16, 1939 Johnson Sept. 17, 1940 Fasold 'et a1 Aug. 10,1943 Fasold et a1 Aug. 10, 1943 McGrew Nov. 2, 1943 Miller Aug. 29, 1944 FOREIGN PATENTS Country Date Great Britain June 30, 1938 

1. A WEATHER SAID FIRE RESISTANT BITUMINOUS COATING COMPOSITION FOR APPLICATION TO A FELT BASE ROOFING SHEET WHICH COMPRISES A VEHICLE CONSISTTING OF A BITUMINOUS THERMOPLASTIC MATERIAL HAVING INTUMESCIBLE MATERIAL SELECTED FROM THE GROUP CONSISTING UNEXFOLIATED VERMICULITE AND COKING COALS DISPERSED IN SAID VEHICLE IN SUFFICIENT QUANTITY TO REDUCE THE FLOWABILITY OF THE BITUMINOUS VEHICLE WHEN IT IS SUBJECTED TO FLAME CONDITIONS. 